Energy
The VRFB located at Eskom’s research testing and
development facility in Johannesburg, South Africa.
VRFB — the answer
to darkness
South Africa faces serious power supply challenges, which has seen the return of load-shedding. Such
challenges illustrate a need for alternative technologies that will cater to the country’s growing energy
demands, writes Dineo Phoshoko.
T
he answer to the country’s power supply problems could
lie in flow battery technology in the form of the vanadium
redox flow battery (VRFB). At the beginning of 2019,
AIM-listed Bushveld Minerals’ energy subsidiary, Bushveld Energy,
commissioned a VRFB for testing at Eskom’s research testing and
development facility in Rosherville, Johannesburg. The battery has a
peak power of 120kW and a peak energy of 450kWh.
The capacity of the energy is determined by the volume of
electrolyte, and the power rating is determined by the active
area of the electrodes. The energy capacity is adjustable and
can be increased by scaling up the size of the electrolyte tanks.
Replacement of the electrolyte immediately recharges the battery.
Vanadium and flow batteries
In their article “Emerging electrochemical energy conversion and
storage technologies”, authors Sukhvinder Badwal, Sarbjit Giddey,
Christopher Munnings, Anand Bhatt, and Anthony Hollenkamp
describe a flow battery as a rechargeable battery that stores energy in
at least one electroactive species, dissolved into liquid electrolytes. Pat Frampton, Bushveld Energy’s chief technical engineer,
explained that the development of Eskom’s VRFB project started
10 years ago, with two batteries developed for testing four years
ago. Frampton believes that VRFBs have an edge compared to
other batteries such as lithium, sodium nickel chloride, and lead
batteries. “The reason vanadium is particularly good is because of
the relative ratio between power and energy,” Frampton said.
A VRFB depends on a liquid vanadium electrolyte to store energy
in separate storage tanks and not in the battery’s power cell, unlike
conventional batteries. The electrolytes are pumped through a
stack of power cells where an electromechanical reaction occurs,
therefore producing electricity. Frampton explained how in two cycles, the battery would assist solar
energy with load shifting, especially during peak periods when power
usage is high. Typically, normal utility use is between 6:00 and 9:00,
which is the peak period for high electricity consumption. In this case,
the battery would be charged throughout the night during the off-peak
What is a VRFB and how does it work?
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